Vertical water gardens exist, but those with submersible air pumps present potential electrical safety problems.
Some vertical garden planters require extra sprinkler feeds at the top of the vertical garden, which adds unnecessary moving parts, as in U.S. Pat. No. 4,419,843 of Johnson.
U.S. Pat. No. 4,447,983 of Shineda uses a closed air valve such as used in automobile tires at the top of the flow chamber. In Shineda, the pressurized air from the air pump is released through a valve which is opened by upward movement of a float 34, but this requires moving parts and highly pressurized air.
In addition, U.S. Pat. No. 4,033,072 of Kobayashi describes an air inlet for a planter which has a check valve 34, with moving parts, which could present an unexpected failure mode when it sticks in the open or closed position. It requires compressed air to be introduced into the mixing tube with fluid pressure in the reservoir increasing so that the check valve can move to an open position, which are features not required by the present invention.
Additionally, U.S. Pat. No. 6,615,542 of Ware includes cylindrical planter ports which are placed obliquely outward from vertical columns. The fact that the cylinder ports are not truncated means that the outer end is slanted also. This tends to cause plant material to climb outward and droop downward.
In addition, in configurations with non-truncated cylindrical planter ports the water only flows up to the horizontal point of the lowest portion of the opening, so that if water is splashed upward, or is driven into root or plant-growing material above the water line, the nutrient salts in the mixture will accumulate as leachate and cause fertilizer burn to the plant material.